1. Field of the Invention
The present invention relates to mixtures of redispersible polymer powders and dry-mix formulations of cement containing the redispersible polymer powders, in particular dry-mix formulations containing alumina rich cement.
2. Introduction
Dry-mix cement formulations (or simply “dry-mix formulations”) are valuable for transporting and storing cement composition in a ready-to-mix and use state. Generally, preparation of a mortar from a dry-mix formulation merely requires addition of water. Dry-mix formulations often comprise redispersible polymer powder (RDP) additives to improve properties of a mortar prepared by mixing the dry-mix formulation with water. A common RDP additive used in dry-mix formulations are redispersible particles of vinyl acetate ethylene (VAE) copolymers and blends of VAE and vinyl ester of versatic acid (VeoVA) copolymers (VAE/VeoVA copolymers). These types of polymer additives are useful for enhancing working properties of the dry-mix as it is dispersed in water to form a mortar, in application of the mortar, and/or by increasing strength and flexibility of the resulting mortar by forming a polymer network within the resulting mortar.
Dry-mix formulations containing alumina rich cement are of particularly interest. Alumina-rich cement provides faster set times relative to Portland cements. Alumina-rich cement formulations are especially desirable for use in premium cement tile adhesives (CTA) and also in waterproofing membranes, grouts and self leveling underlayments. Alumina rich cement contains an alumina (Al2O3) content of greater than 30 weight-percent (wt %), preferably 40 wt % or more, more preferably 55 wt % or more and most preferably 70 wt % or more based on the total weight of the alumina rich cement.
It is a continuous desire in the industry of dry-mix formulations to improve mortar properties and enhance end-use performance of mortars. For example, it is desirably to have a longer quick open time in order to increase the working time of a mortar. It is also desirable to decrease the set time of a mortar to allow workers to move from application of a mortar during construction to subsequent stages in construction more quickly, which improves productivity. It is yet further desirable to decrease the required water load for a dry-mix formulation, which corresponds to how much water is required to achieve optimal mortar properties. It is also generally desirable to minimize colloidal stabilizer that accompanies RDP additives into a dry-mix formulation because colloidal stabilizers can interfere with the performance of the RDP in enhancing mortar properties.
At the same time, it is desirable to retain dry-mix formulations as close to current and well accepted formulations as possible. This is desirable to keep costs down and to avoid dramatically changing current industry practices, which can require extensive testing and qualifications to confirm industry standards are still met. For example, the current dominant RDP technology for dry-mix cement formulations is based on VAE and VAE/VeoVA copolymers. It is also desirable to achieve the benefits of alumina rich cement with lower concentrations of alumina rich cement.